An irreversible cycle model of the micro-/nanoscaled Otto engine cycle with internal friction loss is established. The general expressions of the work output and efficiency of the cycle are calculated based on the finite system thermodynamic theory, in which the quantum boundary effect of gas particles as working substance and the mechanical Casimir effect of gas system are considered. It is found that, for a micro-/nanoscaled Otto cycle devices, the work output Wand efficiency eta of the cycle can be expressed as the functions of the temperature ratio tau of the two heat reservoirs, the volume ratio r(V) and the surface area ratio r(A) of the two isochoric processes, the dimensionless thermal wavelength lambda and other parameters of cycle, while for a macroscaled Otto cycle devices, the work output W-0 and efficiency eta(0) of the cycle are independent of the surface area ratio r(A) and the dimensionless thermal wavelength lambda. Further, the influence of boundary of cycle on the performance characteristics of the micro-/nanoscaled Otto cycle are analyzed in detail by introducing the output ratio W/W-0 and efficiency ratio eta/eta(0). The results present the general performance characteristics of a micro-/nanoscaled Otto cycle and may serve as the basis for the design of a realistic Otto cycle device in micro-/nanoscale. (C) 2010 Elsevier Ltd. All rights reserved.